docs: def reindex(self):
          """Squeeze the indices of this blackboxing to ``0..n``.
  
          Returns:
              Blackbox: a new, reindexed |Blackbox|.
  
          Example:
              >>> partition = ((3,), (2, 4))
              >>> output_indices = (2, 3)
              >>> blackbox = Blackbox(partition, output_indices)
              >>> blackbox.reindex()
              Blackbox(partition=((1,), (0, 2)), output_indices=(0, 1))
          """
          _map = dict(zip(self.micro_indices, reindex(self.micro_indices)))
          partition = tuple(
              tuple(_map[index] for index in group)
              for group in self.partition
          )
          output_indices = tuple(_map[i] for i in self.output_indices)
  
          return Blackbox(partition, output_indices)